Another limitation of our study [1] was the lack of patients with relapse. We have meanwhile gathered more experience with the use of this marker in this regard. In our experience, a rise of circulating endothelial cells is observed in patients who relapse although the elevation is rather moderate and protracted (unpublished data). Another application is the use of circulating endothelial cells as a screening test whenever other tests do not suffice. We use this marker as an adjunctive tool similar to ANCA measurements. It must be emphasized, however, that both augment rather than replace clinical assessment.